Absorptive glass

ABSTRACT

Glass having an extremely high absorption coefficient for incident light in fiber optical image transfer devices and working compatibility with conventional light-conducting glasses used in the manufacture of such devices. The glass consists essentially of lanthanum trioxide, boron oxide, manganese dioxide, a colorant and glass forming, modifying and stabilizing ingredients.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Glass compositions relating more particularly to improved lightabsorptive glass materials for use in fiber optical image-transferdevices.

2. Description of Prior Art

Fiber optical image-transfer devices such as are shown in applicationSer. No. 238,372 now U.S. Pat. No. 3,387,959, entitled Fiber OpticalImage Transfer Devices and Method of Making the Same, filed Nov. 19,1962 and assigned to the same assignee as the present invention, havelight-conducting optical fibers secured in bundled side-by-side relationwith each other. Each optical fiber comprises a core filament,frequently formed of a lanthanum borate glass material surrounded by acladding of a different glass material. The core filament material is ofrelatively higher refractive index than the fiber cladding material.Interspersed within this bundle between the light-conducting opticalfibers are light-absorbing fibers each having a core filament ofabsorptive glass material surrounded by a cladding of a differentlight-transmitting glass material. Usually the same material is used forcladding both the light-conducting and light-absorbing fibers so thatthe claddings of both types of fibers can be easily fused together toform a vacuum-tight bundle of fibers. It will be understood that thecore filaments and fiber cladding materials must be of compatible fusingtemperature, drawing temperature, viscosity, coefficient of thermalexpansion and the like so that the filament cores can be clad byconventional techniques and so that the fibers can be readily fusedtogether. Particularly where the light-conducting fibers are to be drawntogether with light-absorbing fibers to form multifiber units, it isdesirable that the cores of both types of fibers be of compatible fusingtemperature, drawing temperature etc. It will also be understood that,in order to perform their function as described in said copendingapplication, the light-absorbing core materials are preferably adaptedfor extremely high absorption of incident light.

SUMMARY OF THE INVENTION

The absorptive glass material provided by this invention incorporatesmixtures of lanthanum trioxide (La₂ O₃) and boron oxide (B₂ O₃) as itsprincipal glass forming ingredients. Lanthanum trioxide is preferablyused within the range from approximately 15 to 33 weight percent of theglass composition and boron trioxide is preferably used within the rangeof approximately 9 to 22 weight percent of the composition. Such glassmaterials can also incorporate silicon dioxide (SiO₂) within the rangeof approximately 0 to 8 weight percent as a glass forming ingredient ofthe materials. The glass compositions of this invention further embodybarium oxide (BaO) as a modifier essential to the formation of the glassmaterial, this ingredient preferably being incorporated within the rangefrom approximately 4 to 30 weight percent. In addition, these glassmaterials can also incorporate other glass modifiers such as cadiumoxide (CdO) within the range from about 0 to 12 weight percent and zincoxide (ZnO) within the range from approximately 0 to 4 weight percent.

These novel and improved glass materials also include zirconium dioxide(ZrO₂) and tantalum oxide (Ta₂ O₅) as stabilizers. Zirconium dioxide ispreferably incorporated within the range from approximately 0 to 8weight percent and tantalum oxide is incorporated within the range fromabout 7 to 12 weight percent. Other glass stabilizing ingredients canalso be used within the scope of this invention. For example, tungstentrioxide (WO₃) can be incorporated in the glass materials within therange from about 0 to 6 weight percent of the glass composition; thoriumdioxide (ThO₂) can be included in the materials within the range fromabout 0 to 2 weight percent; aluminum oxide (A1₂ O₃) can be used,particularly to improve the durability of the glasses, within the rangefrom about 0 to 0.6 weight percent; and columbium oxide (Cb₂ o₅) canalso be used within the range from approximately 0 to 9 weight percent.

In accordance with this invention, the highly absorptive lanthanumborate glasses must incorporate manganese dioxide (MnO₂) within therange from about 15 to 25 weight percent in order to attain the highoptical density desired. In addition, these glass materials can alsoincorporate one or more other colorants selected from the groupconsisting of chromium oxide (Cr₂ O₃), ferric oxide (Fe₂ O₃), cobaltoxide (Co₃ O₄), cupric oxide (CuO) and nickelic oxide (Ni₂ O₃) forfurther increasing the optical density of the glass materials. Thechromium oxide content of the materials is preferably limited to therange from 0 to 0.5 weight percent of the glass composition; the ferricoxide content is limited within the range from about 0 to 5 weightpercent; the cobalt oxide content is limited to the range from about 0to 4 weight percent; the cupric oxide content is limited to the rangefrom about 0 to 5 weight percent; and the nickelic oxide content islimited to the range from about 0 to 3 weight percent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various ingredients of the glass materials of this invention can bevaried within the limits as described so that the calculated oxidecomposition of the glass materials can be set forth as follows:

                         Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   15 to 33                                               Boron Oxide (B.sub.2 O.sub.3)                                                                        9 to 22                                                Silicon Dioxide (SiO.sub.2)                                                                          0 to 8                                                 Barium Oxide (BaO)     4 to 30                                                Cadmium Oxide (CdO)    0 to 12                                                Zinc Oxide (ZnO)       0 to 4                                                 Zirconium Dioxide (ZrO.sub.2)                                                                        0 to 9                                                 Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    7 to 12                                                Tungsten Trioxide (WO.sub.3)                                                                         0 to 6                                                 Thorium Dioxide (ThO.sub.2)                                                                          0 to 2                                                 Aluminum Oxide (Al.sub.2 O.sub.3)                                                                    0 to .6                                                Columbium Oxide (Cb.sub.2 O.sub.5)                                                                   0 to 9                                                 ______________________________________                                    

said glass material including colorants selected from the groupconsisting of

                         Percent by Weight                                        ______________________________________                                        Manganese Dioxide (MnO.sub.2)                                                                        15 to 25                                               Chromium Oxide (Cr.sub.2 O.sub.3)                                                                      0 to 0.5                                             Ferric Oxide (Fe.sub.2 O.sub.3)                                                                      0 to 5                                                 Cobalt Oxide (Co.sub.3 O.sub.4)                                                                      0 to 4                                                 Cupric Oxide (CuO)     0 to 5                                                 Nickelic Oxide (Ni.sub.2 O.sub.3)                                                                    0 to 3                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof glass of 100 microns thickness at least for light of wavelengthsbetween 0.4 and 0.6 microns.

Although various conventional ingredients can be employed for forming aglass material having calculated oxide compositions as set forth above,a preferred raw batch composition for achieving the glass material ofthis invention could comprise the raw batch ingredients as follows:

EXAMPLE A (BATCH)

                         Parts by Weight                                          ______________________________________                                        Lanthanum Trioxide     112.24                                                 Boron Trioxide         74.52                                                  Barium Nitrate Ba(NO.sub.3).sub.2                                                                    46.04                                                  Zirconium Dioxide      27.08                                                  Tantalum Pentoxide     42.32                                                  Tungsten Trioxide      21.16                                                  Manganese Dioxide      93.60                                                  Chromium Trioxide      2.00                                                   Total                  418.96                                                 ______________________________________                                    

According to this invention, the described raw batch ingredients areweighed out and mixed in conventional manner and are placed in aplatinum crucible. The crucible is then placed in an electrical furnaceof the silicon carbide resistance type or other conventional furnace andthe batch ingredients are melted at a temperature of 2500°- 2700° F. Asthe glass batch melts, additional batch material is added to thecrucible until the desired batch size is attained. No special atmosphereis required in most cases but the noted batch ingredients will normallyestablish a neutral or mildly oxidizing atmosphere. On the other hand,as will be understood, a reducing atmosphere is preferred where ferricoxide is employed as a colorant. After the batch ingredients have beenmelted in this manner, the batch is maintained at a temperature of about2500° F for fining of the batch in conventional manner. For a 10 poundbatch size, this fining will require from 1 to 3 hours. The batch isthen cast at a temperature from 2400°-2450° F., is annealed for severalhours at temperatures from 1050°-1150° F., and can be slowly cooled toroom temperature overnight.

The calculated oxide composition of glass prepared from such batchingredients is as follows:

    Example A                                                                                          Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   28.06                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        18.63                                                  Barium Oxide (BaO)     6.77                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        6.77                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    10.58                                                  Tungsten Trioxide (WO.sub.3)                                                                         5.29                                                   Manganese Dioxide (MnO.sub.2)                                                                        23.40                                                  Chromium Oxide (Cr.sub.2 O.sub.3)                                                                    0.50                                                                          100.00                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof said glass of 100 microns thickness at least for light of wavelengthsfrom 0.4 to 0.6 microns.

Other examples illustrating calculated oxide compositions of absorptiveglass materials provided by this invention are as follows:

    Example B                                                                                          Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   20.17                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        18.49                                                  Barium Oxide (BaO)     4.87                                                   Cadmium Oxide (CdO)    10.65                                                  Zinc Oxide (ZnO)       3.73                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        6.77                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    7.61                                                   Tungsten Trioxide (WO.sub.3)                                                                         3.81                                                   Manganese Dioxide (MnO.sub.2)                                                                        23.40                                                  Chromium Oxide (Cr.sub.2 O.sub.3)                                                                    0.50                                                                          100.00                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof glass of 100 microns thickness at least for light of wavelengths from0.4 to 0.6 microns.

    Example C                                                                                          Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   31.33                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        20.81                                                  Barium Oxide (BaO)     7.56                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        7.56                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    11.83                                                  Tungsten Trioxide (WO.sub.3)                                                                         5.91                                                   Manganese Dioxide (MnO.sub.2)                                                                        15.00                                                                         100.00                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof glass of 100 microns thickness at least for light of wavelengths from0.4 to 0.6 microns.

Other examples of glass compositions provided by this invention, all ofwhich provide optical densities of at least 0.25 for light ofwavelengths from 0.4 to 0.6 microns, are as follows:

    Percent by Weight                                                             Ex.D         Ex.E     Ex.F     Ex.G   Ex.H                                    ______________________________________                                        La.sub.2 O.sub.3                                                                      26.77    26.21    26.21  30.22  15.50                                 B.sub.2 O.sub.3                                                                       17.77    17.40    17.40  20.07  9.58                                  SiO.sub.2                                                                             --       --       --     --     7.09                                  BaO     6.46     6.33     6.33   7.30   28.86                                 ZrO.sub.2                                                                             6.46     6.33     6.33   7.30   --                                    Ta.sub.2 O.sub.5                                                                      10.10    9.89     9.89   11.41  9.27                                  WO.sub.3                                                                              5.04     4.94     4.94   5.70   4.25                                  ThO.sub.2                                                                             --       --       --     --     1.84                                  Al.sub.2 O.sub.3                                                                      --       --       --     --     0.53                                  Cb.sub.2 O.sub.5                                                                      --       --       --     --     8.08                                  MnO.sub.2                                                                             23.40    23.40    23.40  15.00  15.00                                 Cr.sub.2 O.sub.3                                                                      0.50     0.50     0.50   --     --                                    Fe.sub.2 O.sub.3                                                                      --       --       5.00   --     --                                    Co.sub.3 O.sub.4                                                                      3.50     --       --     --     --                                    CuO     --       5.00     --     --     --                                    Ni.sub.2 O.sub.3                                                                      --       --       --     3.00   --                                            100.00   100.00   100.00 100.00 100.00                                ______________________________________                                    

    Percent by Weight                                                             Ex.I         Ex.J     Ex.K     Ex.L   Ex.M                                    ______________________________________                                        La.sub.2 O.sub.3                                                                      28.12    28.23    30.96  30.22  30.96                                 B.sub.2 O.sub.3                                                                       18.68    18.75    20.56  20.07  20.56                                 BaO     6.79     6.82     7.48   7.30   7.48                                  ZrO.sub.2                                                                             6.79     6.82     7.48   7.30   7.48                                  Ta.sub.2 O.sub.5                                                                      10.62    10.66    11.68  11.41  11.68                                 WO.sub.3                                                                              5.30     5.32     5.84   5.70   5.84                                  MnO.sub.2                                                                             23.40    23.40    15.00  15.00  15.00                                 Cr.sub.2 O.sub.3                                                                      0.30     --       --     --     --                                    Co.sub.3 O.sub.4                                                                      --       --       1.00   --     --                                    CuO     --       --       --     3.00   --                                    Ni.sub.2 O.sub.3                                                                      --       --       --     --     1.00                                          100.00   100.00   100.00 100.00 100.00                                ______________________________________                                    

The absorptive glasses of this invention are durable and stable and arechemically and thermally compatible with conventional glasses employedin optical fibers. The glasses are of good quality and are substantiallyfree of bubbles, seeds and other inclusions. Generally, the glasses donot tend to bloom (form surface films) or to devitrify as do otherextremely absorptive glasses. In particular, the improved absorptiveglasses have fusing temperatures, drawing temperatures, viscosities andcoefficients of thermal expansion compatible with the lanthanum borateglasses conventionally employed as core materials in light-conductingoptical fibers. The absorptive glasses can be readily drawn, clad andfused together with conventional optical fiber glass materials, and,when embodied in fiber optical image transfer devices such as noted inthe aforesaid copending application, can be conveniently ground andpolished by conventional techniques. These novel glass materials arealso chemically compatible with phosphors and the like conventionallyemployed with fiber optical image-transfer devices.

It will be understood that the examples of glass materials describedherein have been described by way of illustration and that thisinvention includes all modifications and equivalents of said glasseswhich fall within the scope of the appended claims.

We claim:
 1. An absorptive glass material having a calculated oxidecomposition comprising

                         Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   15 to 33                                               Boron Oxide (B.sub.2 O.sub.3)                                                                         9 to 22                                               Silicon Dioxide (SiO.sub.2)                                                                          up to 8                                                Barium Oxide (BaO)      4 to 30                                               Cadmium Oxide (CdO)    up to 12                                               Zinc Oxide (ZnO)       up to 4                                                Zirconium Dioxide (ZrO.sub.2)                                                                        up to 9                                                Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                     7 to 12                                               Tungsten Trioxide (WO.sub.3)                                                                         up to 6                                                Thorium Dioxide (ThO.sub.2)                                                                          up to 2                                                Aluminum Oxide (Al.sub.2 O.sub.3)                                                                     up to 0.6                                             Columbium Oxide (Cb.sub.2 O.sub.5)                                                                   up to 9                                                ______________________________________                                    

said glass material including colorants selected from the groupconsisting of

                         Percent by Weight                                        ______________________________________                                        Manganese Dioxide (MnO.sub.2)                                                                         15 to 25                                              Chromium Oxide (Cr.sub.2 O.sub.3)                                                                      up to 0.5                                            Ferric Oxide (Fe.sub.2 O.sub.3)                                                                      up to 5                                                Cobalt Oxide (Co.sub.3 O.sub.4)                                                                      up to 4                                                Cupric Oxide (CuO)     up to 5                                                Nickelic Oxide (Ni.sub.2 O.sub.3)                                                                    up to 3                                                ______________________________________                                    

said glass having an optical density of at least 0.25 at least for lightof wavelengths between 0.4 and 0.6 microns.
 2. An absorptive glassmaterial having a calculated oxide composition comprising

                         Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   28.06                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        18.63                                                  Barium Oxide (BaO)     6.77                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        6.77                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    10.58                                                  Tungsten Trioxide (WO.sub.3)                                                                         5.29                                                   Manganese Dioxide (MnO.sub.2)                                                                        23.40                                                  Chromium Oxide (Cr.sub.2 O.sub.3)                                                                    0.50                                                   Total                  100.00                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof said glass of 100 microns thickness at least for light of wavelengthsfrom 0.4 to 0.6 microns.
 3. An absorptive glass material having acalculated oxide composition comprising

                         Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   20.17                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        18.49                                                  Barium Oxide (BaO)     4.87                                                   Cadmium Oxide (CdO)    10.65                                                  Zinc Oxide (ZnO)       3.73                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        6.77                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    7.61                                                   Tungsten Trioxide (WO.sub.3)                                                                         3.81                                                   Manganese Dioxide (MnO.sub.2)                                                                        23.40                                                  Chromium Oxide (Cr.sub.2 O.sub.3)                                                                    0.50                                                   Total                  100.00                                                 ______________________________________                                         said glass having an optical density of at least 0.25 in a sample sheet of     said glass of 100 microns thickness at least for light of wavelengths from     0.4 to 0.6 microns.


4. An absorptive glass material having a calculated oxide compositioncomprising

                         Percent by Weight                                        ______________________________________                                        Lanthanum Oxide (La.sub.2 O.sub.3)                                                                   31.33                                                  Boron Oxide (B.sub.2 O.sub.3)                                                                        20.81                                                  Barium Oxide (BaO)     7.56                                                   Zirconium Dioxide (ZrO.sub.2)                                                                        7.56                                                   Tantalum Oxide (Ta.sub.2 O.sub.5)                                                                    11.83                                                  Tungsten Trioxide (WO.sub.3)                                                                         5.91                                                   Manganese Dioxide (MnO.sub.2)                                                                        15.00                                                  Total                  100.00                                                 ______________________________________                                    

said glass having an optical density of at least 0.25 in a sample sheetof glass of 100 microns thickness at least for light of wavelengths from0.4 to 0.6 microns.